State-of-the-art and highly reliable natural gas engine-driven air compressors are available from several reliable suppliers. This site provides an updated listing under the Manufacturers and Product link.
These air compressors are available in capacities ranging from 50 to 600 horsepower in a variety of configurations for many different applications and are available in air-cooled and water-cooled systems for operations at pressures up to 150 psig.
The Buyers guide available here provides information on system selection, system design, manufacturers & products, and system installation, operation, maintenance and system optimization. The guide incorporates typical information necessary to identify options and evaluate their preliminary feasibility for specific applications. OEMs and their agents will be glad to provide any additional information you might need.